Journal of Materials in Civil Engineering

This paper presents an equation that governs the stress-strain behavior of any metallic material subjected to uniaxial stress tests under any stress or strain rate and under any temperature; thus, it can be considered as a universal model of uniaxial stress-strain behavior in which the classical models—lineal, perfectly plastic, elastic perfectly plastic, or those that obey a power law—are regarded as simple limiting cases of such an equation. Consequently, the equation represents one line only, which is continuous and differentiable at every point, and it is not necessary to draw it separately in sections to characterize the different phases or singular points that appear in the curves of building steel at room temperature, including different yield peaks (upper and lower), the plastic plateau, or even the Portevin-Le Chatelier effect that such a plateau often presents.

Ultrahigh-performance concrete (UHPC) exhibits several properties that make it appropriate for the rehabilitation of concrete structures. In this investigation, the application is focused on bridge deck overlays, but the study is equally applicable to other rehabilitation applications. Its negligible permeability makes this material suitable as a protective barrier that prevents any water or chemical penetration into the substrate. In addition, its ultra-high compressive strength and post-cracking tensile capacity could provide an improvement to the bearing capacity. However, for extensive acceptance, it has to be demonstrated that the bond between UHPC and normal strength concrete (NSC) offers a good long-term performance under a variety of operating conditions. The UHPC-NSC interface can experience high tensile, shear, and compressive stresses at both early and later life stages and the environmental conditions inherent to the operating environment. The success of the rehabilitation will depend on whether the bond interface can withstand the stress combinations subjected throughout its service-life owing to material incompatibilities or applied loads. This paper explores the bond characteristics between UHPC and NSC under varying stress configurations and environmental conditions. Variables, such as roughness degree of the concrete substrates, age of bond, exposure to freeze-thaw cycles and wetting conditions of the concrete substrate, were included in this study. The combination of splitting tensile test with 0, 300, 600, and 900 freeze-thaw cycles was carried out to assess the bond performance under severe environmental conditions. The slant-shear test was conducted with different interface angles to provide a broader understanding of the bond performance under several combinations of compression and shear stresses. In addition, measurements of the bond tensile strength, using the pull-off test, were used to provide data that can be correlated in the future with the other tests that only can be used in the laboratory. The experimental program showed that the bond performance between UHPC and NSC is adequate for bridge overlay applications, regardless of the degree of roughness of the concrete substrate, the age of the composite specimens, the exposure to freeze-thaw cycles, and the different loading configurations. The controlling factor was the strength gain of the UHPC at early ages relative to the strengths of the substrate.

Some project specifications allow the substitution of compressive strength for flexural strength testing for the quality control of projects in which flexural strength is the critical type of strength, such as for pavements. There are certain errors during the production of concrete and aggregate in which the use of compressive strength quality control testing may not be sufficiently sensitive to detect significant changes in flexural strength. A survey of concrete production operations revealed that numerous production errors (variables) commonly occur in practice. Thirteen of these plant production variables were examined for their effects on changes in compressive strength relative to flexural strength. Combining the results of the present study with data reported from the literature indicated that compressive strength may be less sensitive than flexural strength to changes in aggregate particle shape and texture, gradation, maximum aggregate size, aggregate source mineralogy, mineral filler/dust content, deleterious material, and possibly aggregate coatings and water-cementitious material ratio. Thus, under certain conditions, it may be unconservative to use compressive strength testing in lieu of flexural strength testing for quality control.

Pavement macrotexture is a major factor that influences surface functions. This work characterizes the fractal and multifractal properties of asphalt pavement macrotexture using three-dimensional (3D) measurements. A handheld 3D laser scanner is introduced to scan pavement macrotexture in situ. It is verified that the 3D scanning method has good repeatability. Field tests are conducted at 37 highway and urban road sections, which include six types of asphalt pavement surfaces, dense asphalt concrete (DAC), stone matrix asphalt (SMA), rubber asphalt concrete (RAC), ultrathin wearing course (UTWC), microsurfacing (MS), and open graded friction course (OGFC). Three indicators are selected to capture the fractal and multifractal properties of pavement macrotexture: (1) fractal dimension ($D$); (2) the differences between the two endpoints of multifractal spectrum in horizontal; and (3) vertical directions [$\mathrm{\Delta }\alpha$ and $\mathrm{\Delta }f(\alpha )$]. These indicators can quantify the general irregularity, the steepness difference between the flattest parts and the steepest parts, and the difference in total area between the flattest parts and the steepest parts of pavement macrotexture, respectively. The correlation coefficients between $D$, $\mathrm{\Delta }\alpha$, $\mathrm{\Delta }f(\alpha )$ and the mean texture depth (MTD) are 0.8423, 0.7620, and 0.8732, respectively. The correlation coefficient between $\mathrm{\Delta }f(\alpha )$ and friction coefficient at the speed of $60\mathrm{km}/\mathrm{h}$ (DFT60) is 0.6996. It is 0.6639 when relating $D$ and DFT60. However, when relating MTD to DFT60, it is only 0.4483. It is shown that $\mathrm{\Delta }f(\alpha )$ and $D$ derived from 3D measurement have some advantages over MTD in skid resistance evaluation. The fractal and multifractal indicators enriched the options for macrotexture evaluation.

This research focused on modeling the first-crack load as a function of steel-fiber fraction to optimize the steel-fiber fraction through load-deflection response and flexural behavior of steel-fiber-reinforced concrete (SFRC). Specifically, this study involved an experimental method to examine simultaneous flexural load-deflection response measurements on normal portland cement concrete and steel-fiber-reinforced concrete. Other basic tests were addressed to characterize fresh mix and constituent material properties. Regression models were developed to predict the following: (1) first-net deflection; (2) net deflection at any applied load; and (3) first-crack load at different mix combinations of steel fiber. Results from this investigation showed that in the flexural load-deflection response tests, SFRC beams experienced an increase in first-crack net deflection. In addition, Inclusion of steel fiber at 0.64% by volume of concrete did not cause a significant change in the first-crack strength.

In this research, the ability of pervious concrete pavement material to reduce pollutant concentrations and purify water was investigated. This project mainly aims to study the ability of pervious concrete pavement material to reduce pollutant concentrations such as those in diluted sulfuric acid, seawater, and motor oil. The results demonstrated that the ability of pervious concrete pavement material to reduce pollutant concentrations and purify water was effective in diluted sulfuric acid, artificial seawater, and motor oil tests. After flowing through pervious concrete pavement, a diluted sulfuric acid solution (pH value 2.0) could dramatically increase its pH value to approximately 7.0. A pervious concrete pavement system could greatly decrease the content of an artificial seawater solution (salinity 36%) to about 1%, and the oil content of motor oil combined with certain types of water could also be significantly decreased to 1%. The study demonstrates that pervious concrete pavement holds potential for environment conservation and hydrologic consideration.

Perpetual pavements, if properly designed and rehabilitated, last longer than 50 years without major structural rehabilitation. The fatigue endurance limit (EL) is a key parameter for designing perpetual pavements to mitigate bottom-up fatigue cracking. The endurance limit has not been completely implemented in the Mechanistic Empirical Pavement Design Guide software, currently known as AASHTOWare Pavement ME Design software. This study was conducted as part of the National Cooperative Highway Research Program (NCHRP) project 9-44A to develop a framework and mathematical methodology to determine the EL for hot mix asphalt (HMA) using the uniaxial tension-compression fatigue test. In this unique procedure, the EL is defined as the allowable tensile strains at which a balance takes place between the fatigue damage during loading and the healing during rest periods between loading pulses. The viscoelastic continuum damage model was applied into the data analysis. This study also included the development of a uniaxial fatigue test method and the associated data acquisition computer programs to conduct the test with and without rest period. The laboratory testing program consisted of dynamic modulus testing to estimate the viscoelastic properties of the asphalt mixtures and a uniaxial fatigue test experiment conducted with and without rest periods. Five factors that affect the fatigue and healing behavior of asphalt mixtures were evaluated: asphalt content, air voids, temperature, rest period, and tensile strain. On the basis of the test results, a pseudo stiffness ratio (PSR) regression model was developed as a function of the five factors and the number of loading cycles. The EL was defined when PSR is equal to 1.0 (net damage is equal to zero). The results from the sensitivity analysis showed rational relationships between the EL and investigated factors. The EL value was observed to increase by increasing temperature, asphalt content, and rest periods, whereas it decreased when air voids increased.

This study outlines statistical analyses carried out to investigate the effect of test temperature on results from Hamburg wheel-tracking device (HWTD) tests. The Hamburg test database and aggregate properties database of the Texas Department of Transportation (TxDOT) were examined and merged to provide the basis for statistical analysis. Because the most significant effect of test temperature was on the binder component of the asphalt mixture, the effect of test temperature on the binder type was also investigated. Finally, the influence of test temperatures together with the combined interaction of binder and additive addition is studied. Of the three performance-graded (PG) binders that TxDOT predominantly uses for their surface mixes, this study determined that the influence of temperature on binder performance is most pronounced in PG 64-22 (causing a huge drop in success rate between 40 and 50°C from an 81% pass rate to a 35% rate), whereas PG 76-22 was the most resistant to temperature difference. Test temperature and average deformation were also found to have a positive correlation, and mixes with higher PG binder developed less deformation than low-grade mixes. Finally, this study concluded that in comparing antistripping agent additives, lime performed better than liquid antistripping additives, and liquid antistripping additives performed better than no antistripping agents in HWTD tests. This indicates that lime is the best additive type for stripping (deformation) resistance. It has a pass rate of 81.5%. The next best type is liquid with a 61.2% pass rate.

This paper describes the behavior of geogrid–reinforced concrete members. The application of geogrids in concrete constitutes a new dimension for using geosynthetics in infrastructure. In pavement applications, geogrids have been used to provide confinement, stabilization, and reinforcement of unbound and asphalt concrete layers, as well as interlayers to mitigate reflective cracking. The ultimate objective of studying the behavior of geogrids in concrete members is to assess the feasibility and benefit of using geogrids in thin concrete overlays. The experimental program consisted of testing 21 simply supported plain and geogrid–reinforced beam specimens under four-point bending. The test parameters included three types of geogrids with different aperture shapes, physical and mechanical properties, and material composition. Additionally, two Portland cement concrete mixtures were used: normal and high strength. Results from testing confirm the reinforcing benefit of the geogrids as evidenced from the load-deflection response in terms of postpeak behavior, load capacity, crack mouth opening displacement (CMOD), and failure mode. Conclusions regarding correlations between the failure properties and the properties of the geogrid are made.

The effect of randomly oriented discrete synthetic fiber inclusions on the properties of soils treated with proprietary liquid chemical stabilization additives was evaluated in a laboratory-based investigation. Mercia mudstone, Oxford clay, and limestone quarry fines were stabilized with a proprietary polymer and reinforced with discrete fibers. The findings were compared with untreated and reinforced specimens, which served as the control. Test results showed that the inclusion of randomly oriented discrete synthetic fibers had no significant effect on the compaction characteristics of the soils examined. However, it did result in significant improvements in the toughness of all soils examined and load retention after peak strength for Mercia mudstone and Oxford clay. Polymer/sulphonated oil-stabilized and fiber-reinforced Mercia mudstone and Oxford clay specimens were found to be highly susceptible to moisture, while polymer-stabilized and reinforced limestone quarry fines specimens demonstrated good durability when submerged in water and retained 21 to 33% of their air-cured strengths.

In this study, the use of tire-rubber particles as a replacement for coarse aggregate in concrete is investigated. Rubber has replaced coarse aggregate at content levels of 25, 50, 75, and 100% in concrete by volume. Also, emulsified asphalt (EA) was used to improve the mechanical properties of rubberized concrete. Four different series of concrete mixtures were designed to investigate the effects of the water-cement (w/c) and EA-cement (EA/C) ratios on the properties of rubberized concrete. The slump, air content, dry unit weight, compressive strength, elasticity modulus, and flexural strength have been compared to the corresponding properties of controlled concrete. Consequently, an increase in rubber content leads to a decrease in slump and an increase in air content because of the rough surface of rubber. An increase in rubber content decreases compressive strength, elasticity modulus, and flexural strength because of its lower stiffness and poorer bonding between rubber and the paste matrix. In the case of equal levels of rubber particle content, the addition of EA greatly increases slump. However, the effects of EA on the properties of rubberized concrete, such as air content, strength, and elasticity modulus, are based on the EA/C ratio. A certain level of EA addition can improve the compressive and flexural strength of rubberized concrete. EA addition reduces the elasticity modulus of the concrete. Adding EA is a good way to improve the bonding between rubber particles and cement paste.

The reported study was undertaken to investigate the micromechanical interactions that occur between sprayed seal (chip seal) layer materials in order to examine their relationship to the initiation of flushing. In particular, the deformation patterns of chip seal pavement samples with respect to lateral cyclic loading as well as the changes that occur to the distribution of air voids within a chip seal layer during loading were investigated. The effect of binder volume and air void volume on the development of flushing of the chip seal samples was also investigated. The reported study was based on laboratory testing of chip seal pavement samples (cores) that were obtained from in-service, flushed pavements in New Zealand. The cores, of 200-mm diameter and thicknesses ranging from 32.4 to 55.5 mm, were subjected to varying levels of lateral cyclic loading using a wheel tracking machine and the deformation that had occurred on the surface of the cores was measured. The cores were then scanned using a computed tomography (CT) scanner to examine changes that had occurred to the air void volume of the cores during the wheel tracking test, and the reductions in air void volume were compared with the quantity of flushing that was displayed on the cores. The cores were tested to determine the binder volumes in order to investigate how flushing development was affected by the ratio of binder volume and air void volume. The results from the analyses demonstrated that a strong correlation existed between flushing and air void volume reduction, where a larger reduction in air void volume directly corresponded to a higher amount of flushing. The deformation pattern of the cores indicated the likely state of stability of the chip seal structure, and the state of stability in turn indicated the best method of maintenance that was required for a flushed surface. The study findings demonstrated that the combination of wheel tracking and CT scanning is an extremely effective analysis method that can be used to determine the state of stability of a chip seal and to select the best maintenance treatment for pavement flushing.

This paper presents an image-based testing system called the asphalt foam collapse test (AFCT) to measure parameters that indicate the quality of foamed warm mix asphalt (WMA) binders. The AFCT was used to measure and evaluate various potential quality indicators such as expansion ratio (ER), half-life (HL), and foam index (FI). In addition, this paper introduces a method to calculate the bubble size distribution (BSD) of the bubbles in the foamed WMA. The BSD is then used to introduce a new parameter called the surface area index (SAI) as an indicator of foamed binder quality. It was shown that the SAI is a strong candidate for evaluating foamed WMA binder for coating and workability. Furthermore, this paper presents the effect of water content and air nozzle pressure on the foam properties. The results revealed that the water content and air pressure have a significant influence on the ER, HL, FI, BSD, and SAI. The low water content and low pressure produced foams with smaller bubbles as compared to foams made with high water content and high pressure, which affected the aggregate coating.

Polymer-infused plant roots can be created without soil excavation by infusing polymer into the roots of plants through the easily accessible above-surface plant stems. Efficacy of this technique for use in soil stabilization applications involves assessing the durability of polymer-infused plant roots. Polymer content was determined for infused Artemisia annua plant roots. Durability of these polymer-infused roots was evaluated by mass loss resistance and strength loss resistance of acid-treated samples. Durability in the context of soil stabilization applications was determined by comparing the shear strength of aged samples. Polymer infusions improved the durability of the plant material. Infused plant stems incubated in acid for 15 weeks lost 29% mass, whereas noninfused stems lost 60% mass. Infused roots incubated in acid for 24 h retained a tensile strength of 25 MPa, whereas noninfused acid-treated roots had a tensile strength of 12 MPa. In comparison to plant roots that provided no enhancements to the soil after 8 weeks of aging, polymer-infused plant roots provided 44% enhancement to soil shear strength.

The steel strands in posttensioned (PT) concrete systems are typically embedded inside cementitious grout for protection from the environment. However, strands not embedded in grout have been observed in PT systems. The exposed strand is susceptible to corrosion, and particularly the location where the strand protrudes from the grout (i.e., grout-air-steel interface) is more vulnerable to corrosion. Prediction of the tension capacity ($C_T$) of strands with such interfaces under various exposure conditions is necessary for structural assessment. This prediction could be accomplished by using the data from an experimental program that includes the exposure of strands to various corrosive environments and testing to determine the time-variant residual $C_T$ of these strands. However, these tests are cumbersome and expensive, especially when it is necessary to maintain very high tensile stress conditions during the exposure period to simulate the in-service stress conditions on the strands in PT systems. Similar investigations of unstressed single wires are simpler and less expensive. This paper presents an experimental investigation of the corrosion-induced losses in the $C_T$ of unstressed wires, unstressed strands, and stressed strands. Based on these data, this paper develops probabilistic models to predict the $C_T$ of unstressed wires with grout-air-steel interfaces and subjected to various moisture and chloride conditions. By using these models for wires and the experimental data on strands, two probabilistic models are then developed to predict the $C_T$ of stressed strands based on the $C_T$ of unstressed wires. The developed models can be used to determine the $C_T$ of strands with grout-air-steel interfaces subjected to various exposure conditions, provided the $C_T$ of corresponding wires under those conditions is estimated.

One of the most important factors influencing the durability of asphalt mixtures is moisture-induced damage resulting from the presence and the transport of moisture in pavements. Moisture-induced damage is an extremely complicated phenomenon that is not completely understood but believed to be governed by the interaction of moisture with asphalt mix components (mastic and aggregates). The objective of this study was, therefore, to characterize the sorption and diffusion characteristics of asphalt mastic using gravimetric vapor sorption techniques. Moisture transport, in the hygroscopic region, in asphalt mastics was studied using both static and dynamic gravimetric vapor sorption techniques to determine equilibrium moisture uptake and diffusion coefficients as a function of aggregate and filler types. For the 25-mm diameter thin asphalt mastic films and the testing conditions (23°C and 85% relative humidity) considered, the kinetics of moisture uptake obtained were characteristic of Fickian diffusion with a concentration-dependent diffusion coefficient. Equilibrium moisture uptake and diffusion coefficient estimated from the static measurements were comparable and of the same order of magnitude as those from dynamic sorption techniques. Both measurement techniques ranked the mixes similarly, which suggest either method could be used to characterize moisture transport in asphalt mastics. Equilibrium moisture uptake was relatively higher in mixtures containing granite aggregates compared with limestone aggregate. In contrast, the diffusion coefficient of limestone aggregate mastics was higher than granite. Thus, an inversely proportional relationship exists between moisture uptake and diffusivity of the asphalt mastics studied. The results suggest moisture transport is a function of aggregate type and that both equilibrium moisture uptake and diffusion coefficient are useful in studying moisture susceptibility in asphalt mixtures. The effect of mineral filler type on diffusion coefficient was minimal in the mastics containing granite aggregate but relatively high in mastic samples containing limestone aggregates. Diffusion coefficient was found to increase with sample thickness, which was unexpected because diffusion coefficient (in an isotropic material) is considered an intrinsic property that is independent of sample size. The results suggested anisotropic diffusivity can occur in asphalt mastics and could be attributed to factors, including mineralogy, microstructure, air voids, and the tendency of the aggregates to settle at the bottom of asphalt mastic with time. In addition to characterizing moisture transport in asphalt mastics, the results presented in this paper will be useful as inputs for numerical simulation of moisture damage in asphalt mixtures.

The unintentional initiation of munitions during production, storage, transportation, and handling is among the main sources of explosive hazard. Such unintentional initiation of explosives is termed sympathetic detonation, in which the detonation of a single explosive unit (or warhead) triggers the detonation of another, and subsequently starts a chain reaction. Because of this, the demand for resilient lightweight ammunition-separation systems within shipping or storage containers is increasing. This paper presents the development and testing of a cost-effective lightweight rigid polyurethane foam (RPF) separation system. The scaled gap test approach discussed is used as a practical tool to investigate the initiability of acceptor explosive charges by a blast wave generated from donor charges through the RPF as a blast wave attenuation medium. Different RPF specimens were prepared with different densities and silt particle mix ratios ranging from 0% (no silt) to 30%. The study results demonstrate the capability of the RPF as a lightweight cost-effective technique to attenuate the blast wave effects on acceptor explosives to safe levels.

Engineered cementitious composite (ECC) is a class of high performance cementitious composites with pseudo strain hardening behavior and excellent crack control. Substitution of concrete with ECC can avoid the cracking and durability problems associated with brittleness of concrete. In this paper, two series, totaling six steel reinforced beams with various transverse reinforcement ratios, ECC thicknesses, and shear span-depth ratios were tested under reversed cyclic loading. According to the test results, steel reinforced ECC beams show better seismic performance in terms of load carrying capacity, shear resistance, energy dissipation capacity, and damage tolerance compared with steel reinforced concrete beams. The extent of load capacity improvement strongly depended on the failure mode. Beams failed in shear showed more significant improvement than those failed in flexure. For the ECC/concrete composite beam, strategic application of ECC can lead to an increase of energy dissipation capacity. For the steel reinforced ECC beam without stirrups, final failure occurs in shear. However, the ultimate load capacity and deformation are comparable to the steel reinforced concrete beam with properly designed stirrups, and the failure process is ductile due to the strain hardening behavior of ECC materials.

The lateritic gravel routinely used in the midwest region of Brazil for pavement construction is no longer found near the urban centers. Thus, there is an increasing need for studies of alternative materials to replace it. This study presents an evaluation of the use of fine quarry wastes. An experimental test asphalt pavement was built with conventional materials and a soil–fine quarry waste mixture. Field tests were conducted to assess the behavior of these materials. It was verified that this waste is able to provide the same performance levels for low-volume roads while offering environmental and economic advantages.

In this work we present an analysis of the applicability of ground penetrating radar (GPR) to karstic hazard evaluation in urban areas by means of several case studies. The main objective is to characterize the origin of pathologies in buildings and other facilities, and of subsidence processes, and to identify their causative phenomena in the subsoil. This study involves the analysis of resolution, penetration characteristics and noise affecting GPR signals in urban areas. The analyzed case studies are located in the Central Ebro Basin (NE Spain), where the main hazards are related to mantled karst (solution of evaporites below alluvial deposits). The studied examples show that in areas affected by karst activity with medium to high subsidence rates, interpretation of GPR profiles allows defining collapses, subsidence, surficial repairs (either historical or recent) and underground cavities.

This paper aims to predict the modulus of elasticity $E_c$ of high-strength concrete (HSC) under different in situ curing conditions. Because of the effect of the hydration temperature and the curing condition, the $E_c$ value of HSC measured on moist-cured specimens may not be able to sufficiently represent that of HSC in structures and precast concrete components. This issue is not adequately taken into account in current codes of practice. Equations based on moist-cured specimens may result in a large discrepancy when used to estimate the in situ $E_c$ of HSC. In this study, measured $E_c$ of HSC on member-cured, temperature match–cured, on-site-cured specimens, and drilled cores from large structural members are gathered. The accuracy of selected equations is investigated using the collected data. Based on the investigations, new empirical relations for estimating the $E_c$ of HSC considering the effect of the in situ curing conditions are proposed.

The present research aims to quantify the influence of curing temperature ($T$), amount of lime ($L$), porosity ($\eta$), and porosity/lime ratio ($\eta /L_{iv}$) on the assessment of splitting tensile strength ($q_t$) and unconfined compressive strength ($q_u$) of sand–coal fly ash–lime blends. A series of splitting tensile and unconfined compression tests were carried out in the present work. The results show that increasing curing temperature in the blend, for the whole range of lime studied, increases $q_t$ and $q_u$. A power function fits well as the relation between $q_t$ and $q_u$ with $\eta$, and a linear function fits well the relation between $q_t$ and $q_u$ with L for all curing temperatures of the specimens. It was also shown that the porosity/lime ratio ($\eta /L_{iv}$) is a good parameter in the evaluation of $q_t$ and $q_u$ of the studied blends for the whole range of lime, porosities and temperature studied, at specific amount of coal fly ash (25%) and curing time period (28 days). The volumetric cementitious material content ($L_{iv}$) is adjusted by an exponent (0.30 for all curing temperatures blends) to end in unique correlations for each temperature. For the sand, coal fly ash, lime, moisture content, curing time period and curing temperatures, a unique relationship was achieved linking $q_t$ as well $q_u$ to $\eta ,L_{iv}$ and $T$. For a given curing time period (28 days), the relations $q_t\text{-}\eta /L_{iv}$ and $q_t\text{-}\eta /L_{iv}$ versus $T$ are shown to vary linearly up to a threshold, when asymptotes occur. Finally, the relation between $q_t/q_u$ is a constant for the whole range of $L$, $\eta$ and $T$ studied.

Loose granular sand deposits formed during the land reclamation process are vulnerable to liquefaction upon imparting seismic forces. These loose granular sand fills could encounter bearing failures or compress beyond tolerable limits under static and dynamic loads. To eliminate such failures, loose granular soils require densification to enhance their engineering properties. Deep compaction is the only means to improve these thick deposits of loose sand fill in many foreshore land reclamation projects. Muller resonance compaction (MRC) and vibroflotation are deep vibratory compaction techniques, which are suitable to densify thick layers of loose granular fills. This paper describes the applications of deep compaction vibratory techniques in a mega-land reclamation project in the Republic of Singapore where the efficacy of densification was verified by cone penetration tests (CPT) undertaken in a pilot test area. In the MRC technique, high vibrating energies are used, which results in the whole mass of soil being rearranged, but a weak point was found at the location of the probing point. In vibroflotation, the densified column of soil was found to form at and surrounding the probe point, and the density of the granular soil reduced with distance from the probe point. The aging effect in vibroflotation was found to be significant. Vibroflotation was found to have several advantages compared with the MRC technique. Because of the excess water in the pore spaces caused by the high pressure jetting in vibroflotation, the water pressure dissipation further enhances the densification due to the aging effect.

A plant (jack bean) extract can function as a urease catalyst, similar to those of certain microorganisms such as Sporosarcina pasteurii, which can decompose urea into carbonate and ammonium ions. Carbonate ions decomposed from urea can combine with calcium ions to form calcium carbonate (usually calcite mineral). In this study, calcium chloride, calcium hydroxide, or calcium nitrate was added to urea solution with plant extract, and then mixed with Nakdong River sand to precipitate calcite within the sand-grain matrix. The mixed sand was compacted into a cylindrical specimen and cured for 3 days at room temperature. A specimen without plant extract was prepared for comparison. A series of unconfined compression tests and analytical methods was carried out on sand treated with various amounts of urea and different calcium sources. With increasing amounts of urea, the unconfined compressive strength (UCS) of the sand treated with plant extract increased 10-fold up to 317 kPa, compared to that of the sand without plant extract. Its strength was similar to that of 4% cemented sand with high-early strength portland cement. The strength of the specimen containing calcium chloride was higher than that with calcium hydroxide or calcium nitrate.

The particle size distribution of coal gangue was obtained from a sieving experiment and the representative grading calculated using the statistical values of coarse grain content. A fractal method was proposed and fractal dimension $D$ deduced based on the accumulated mass distribution function. The results indicate that when the value of $D$ is between 1.89 and 2.63, coal gangues are well graded. The use of a fractal method can help to avoid errors associated with calculating grading parameters ($C_u$ and $C_c$) in traditional theory, and the fractal dimension $D$ can also be used to evaluate the compactability of coal gangues and other bulk materials.

This study investigated the compressive strength of double H concrete block masonry prisms. A total of 42 (i.e., nine ungrouted, 15 half-grouted, and 18 full-grouted) specimens were tested under uniaxial compression. The effects of mortar strength, grouting, and grout strength on the compressive strength of the prism were discussed. The test results show that the compressive strength of H-block prisms decreased with an increase of grouting, although the ultimate load of the prisms increased greatly.